1. Field of the Invention
The present invention relates to an improvement of an illumination light source device and a projector provided with the illumination light source device, and a control method of the projector.
2. Description of the Related Art
For instance, for use at a conference and so on, an illumination light source device for a projector for projecting screen information of a personal computer (hereinafter referred to as “PC”) and so on, which has a high luminance discharge lamp (for instance, a super high-pressure mercury lamp) as a light source, is known.
The discharge lamp provides high brightness at low cost, on the other hand, it requires a specific time to emit light steadily after being turned on.
Therefore, it is proposed to put into use a solid-state light-emitting element such as a Red (R), Green (G) or Blue (B) light-emitting diode or an organic EL device as an alternative light source to the discharge lamp.
By applying the solid-state light-emitting device as an illumination light source of a projector, the projector can be started at high speed. At the same time, environmental concerns can be minimized.
As the illumination light source device using the solid-state light-emitting element, for example, an art for projecting a color image is known (for example, refer to JP2011-13316A). The color image projecting technique is such that using a blue laser diode as a first light source and irradiating laser beam emitted from the blue laser diode as excitation light to phosphor. By exciting the phosphor, each RGB colored light is generated. The each RGB colored light is modulated by a liquid crystal light modulation element and so on in every pixel, and then accomplishes color image projection.
The illumination light source device described in JP2011-13316A as mentioned above includes a solid-state light source group having a plurality of solid-state light-emitting sources, a light-condensing optical system which concentrates light from the solid-state light-emitting source group, a collimator optical system which collimates most of light from the light-condensing optical system, a lens integrator which makes uniform an in-plane light intensity distribution of light from the collimator optical system, and a transmission/diffusion optical component which diffuses and transmits light from the light-condensing optical system, disposed adjacent to a condensing position where the light is concentrated by the light-condensing optical system.
In accordance with the illumination light source device described in JP2011-13316A, because macular light can be incident on a lens integrated optical system after being diffused, high luminance illumination light can be obtained and an efficiency of light utilization is enhanced. Therefore, illumination light having even and stable luminous intensity can be obtained.
An illumination light source device is also known (for example, refer to JP2010-85745A). The illumination light source device includes a fluorescent plate having a fluorescent light-emitting part and a transmission/diffusion part, a first light source emitting light of a particular wavelength bandwidth capable of exciting phosphor, and a second light source emitting fluorescent light from the fluorescent plate and the light having a different wavelength bandwidth from the fluorescent light emitted from the fluorescent plate and the light emitted from the first light source. The illumination light source device further includes a light-guiding system which guides the light of each wavelength bandwidth emitted from the fluorescent plate, and a light source-controlling part which controls lighting-up of the first and second light sources respectively.
According to the disclosures of JP2011-13316A and JP2010-85745A, unevenness of brightness (unevenness in luminous intensity) of light used for illumination light to a screen can be reduced. However, due to the configuration that the excitation light is irradiated directly to the phosphor of a phosphor wheel, the irradiation time per one unit (one second) to the phosphor is fixed regardless of a rotation number of the phosphor per one unit of time (one second), so that there is still the possibility of degradation of fluorescent property of the phosphor if excitation light is continuously irradiated to a micro area of the phosphor.
On the other hand, in order to prevent unevenness of brightness of the light which irradiates a screen and unevenness of the brightness (unevenness in luminous intensity) of fluorescent light, it is considered that the light irradiated from the light source is split into a light path used for exciting the phosphor and a light path used for irradiating a screen, and diffusion members are disposed in both light paths. However, if such a construction is simply adopted, there is a disadvantage in that the loss of light intensity of the light emitted from the light source used for excitation of the fluorescent light is large. That is, the efficiency of the fluorescent light is lowered.
In this regard, a light source device having only one diffuser member disposed in the light path used for irradiation to a screen can be considered. However, if such, the generation efficiency of the fluorescent light is reduced, as a result of which the power density of the light from the light source used for the excitation of the phosphor is too high.